10 best mono-split air conditioners in 2026 (134+ compared)

Leading the ARGO mono-split lineup is ARGO Ecowall 12, delivering an overall score of 7.43 points, a cooling capacity of 12000 BTU/h, a cooling energy class of A++, and retailing for around £300.

The ARGO Ecowall 12 is a fixed wall-mounted split-system air conditioner featuring a nominal cooling capacity of 12,000 BTU/h (3.2 kW) and utilizing eco-friendly, low-GWP R32 refrigerant alongside advanced DC Inverter technology. This 3-in-1 multi-functional unit provides cooling, dehumidification (1.4 L/h), and heating with an energy efficiency rating of A++ for cooling and A+ for heating, achieving a seasonal cooling SEER of 6.1.

Runner-up: ARGO Ecowall 9, with an overall score of 7.19 points, a cooling capacity of 9000 BTU/h, a cooling energy class of A++, and a price of around £520.

The best Daikin mono-split air conditioner is Daikin ARXC35C+ATXC35C, with an overall score of 8.22 points, a cooling capacity of 12000 BTU/h, a cooling energy class of A++, and a price of around £400.

The Daikin ATXC35C (indoor unit) and ARXC35C (outdoor unit) is a 12,000 BTU wall-mounted split system air conditioner powered by eco-friendly R-32 refrigerant, delivering a 3.5 kW cooling capacity and a 4.0 kW heating capacity. Its main characteristics include an efficient inverter compressor, a modern flat front panel, an antibacterial catechin air filter, and high energy performance rated at class A++ for cooling (SEER 6.78) and A+ for heating (SCOP 4.43).

Runner-up: Daikin STIWKMONO005, with an overall score of 8.11 points, a cooling capacity of 12000 BTU/h, a cooling energy class of A++, and a price of around £1500.

Explore our dedicated best Daikin air conditioners guide for full model rankings.

Our top-rated Kältebringer mono-split air conditioner is Kältebringer Split Quick Connect 12000 BTU, achieving an overall score of 8.18 points, a cooling capacity of 12000 BTU/h, a cooling energy class of A++, and priced around £850.

The Kältebringer 12000 BTU (3.5 kW) split air conditioner features a DC full inverter compressor, an integrated air-to-air heat pump for both heating and cooling, an eco-friendly R32 or R290 refrigerant system, and integrated Wi-Fi for app and voice control. It operates on a 230V power supply, delivers impressive efficiency with a SEER rating up to 8.5 (Energy Class A+++/A++), features a multi-stage filter system with TitanGold coating, and effectively services spaces up to 55 m² down to a whisper-quiet 19 dB in sleep mode.

Best value alternative: Kältebringer KB35, with an overall score of 8.18 points, a cooling capacity of 12000 BTU/h, a cooling energy class of A++, and a price of around £550.

Ranking first among Olimpia Splendid mono-split models is Olimpia Splendid Aryal S1 E Inverter 12 C, with an overall score of 7.6 points, a cooling capacity of 12000 BTU/h, a cooling energy class of A++, and available for around £310.

The Olimpia Splendid Aryal S1 E Inverter 12 C (OS-K/SEAPH12EI) is a high-wall mono-split heat pump air conditioner operating on eco-friendly R-32 refrigerant with a capacity of 12,000 BTU, delivering a nominal cooling output of 3.52 kW (A++ energy rating, 6.1 SEER) and a heating output of 3.37 kW (A+ energy rating, 4.0 SCOP). Key characteristics and pros include its multi-filtering Air Quality Technology (anti-dust, activated carbon, and cold catalyst filters), a Self-Clean cycle that automatically dries the evaporator to prevent mould, a corrosive-resistant Golden Fin outdoor coil, Wi-Fi connectivity, and versatile operational profiles like Sleep, Silent, and Follow Me modes.

Best value alternative: Olimpia Splendid Aryal S1 E Inverter 10 C, with an overall score of 7.51 points, a cooling capacity of 10000 BTU/h, a cooling energy class of A++, and a price of around £260.

The best Comfee mono-split air conditioner is Comfee TROPICAL 9K, with an overall score of 7.95 points, a cooling capacity of 9000 BTU/h, a cooling energy class of A++, and a price of around £280.

The Comfee TROPICAL 9K is a 9000 BTU monosplit inverter air conditioner featuring an average airflow of 333 m³/h and utilizing eco-friendly R32 refrigerant to cool or heat rooms up to 25 m² with an efficient A++/A+ energy rating. Main characteristics and pros include integrated WiFi app control, a "Follow Me" thermal sensor on the remote for targeted climate control, a dual filtration system (high-density and cold catalyst filters) that eliminates up to 80% of dust and volatile organic compounds, and a durable golden anti-corrosion coating on the heat exchangers.

Runner-up: Comfee MSAF5-18HRDN8-QE, with an overall score of 7.75 points, a cooling capacity of 16000 BTU/h, a cooling energy class of A++, and a price of around £1060.

Topping the electriQ mono-split selection is electriQ iQool12Plus 12000 BTU, earning an overall score of 8.59 points, a cooling capacity of 12000 BTU/h, a cooling energy class of A+++, and costing around £510.

The electriQ iQool 12000 BTU Smart A+++ Split Air Conditioner is a highly efficient wall-mounted system capable of cooling and heating rooms up to 30m² using an eco-friendly R32 refrigerant and a powerful GMCC Toshiba compressor with Super DC Inverter technology. This multi-functional 3-in-1 unit provides 3.8 kW of maximum cooling capacity, 3.8 kW of heating capacity, and a built-in dehumidifier that removes excess moisture, achieving an exceptional SEER rating of 8.5 (A+++) for cooling and a SCOP of 4.6 (A++) for heating.

Runner-up: electriQ iQool9Plus 9000 BTU, with an overall score of 8.25 points, a cooling capacity of 9000 BTU/h, a cooling energy class of A+++, and a price of around £550.

Ranking first among Mitsubishi mono-split models is Mitsubishi MSZ-AY35VGKP+MUZ-AY35VG 12000 BTU, with an overall score of 8.55 points, a cooling capacity of 12000 BTU/h, a cooling energy class of A+++, and available for around £1130.

The Mitsubishi MSZ-AY35VGKP+MUZ-AY35VG is a high-efficiency 12000 BTU inverter split-system air conditioner designed for spaces between 25–35 m². It features an outstanding A+++ energy rating for cooling and A++ for heating, a stellar SEER of 8.7 and SCOP of 4.7, and runs on eco-friendly R-32 refrigerant.

Best value alternative: Mitsubishi MSZ-HR35VF, with an overall score of 7.44 points, a cooling capacity of 12000 BTU/h, a cooling energy class of A++, and a price of around £530.

Browse our dedicated best Mitsubishi air conditioners guide to compare all evaluated models.

The best Toshiba mono-split air conditioner is Toshiba Haori 12000/13000 BTU, with an overall score of 8.18 points, a cooling capacity of 12000 BTU/h, a cooling energy class of A+++, and a price of around £1160.

The Toshiba Haori inverter air conditioner (12000/13000 BTU or 3.5 kW nominal capacity) is a highly efficient, wall-mounted split system using eco-friendly R32 refrigerant. It features a distinct aesthetic defined by interchangeable fabric covers, a premium A+++ energy rating for both cooling and heating, and an exceptionally low indoor noise level down to 19 dB(A).

Runner-up: Toshiba Haori 10000 BTU, with an overall score of 7.99 points, a cooling capacity of 10000 BTU/h, a cooling energy class of A+++, and a price of around £1040.

Discover additional top picks in our full best Toshiba air conditioners guide.